Hybrid automatic repeat request (harq) feedback management based on location information availability and sidelink signal quality for group sidelink communication

ABSTRACT

A receiving user equipment (UE) device transmits a distance-based hybrid automatic repeat request (HARQ) feedback message to a transmitting UE device based on sidelink signal quality when location information is unavailable. The receiving UE device is one of a group of UE devices receiving a groupcast data transmission from the transmitting UE device where the groupcast data transmission comprises a distance-based hybrid automatic repeat request (HARQ) feedback configuration. When location information is unavailable to the receiving UE device, the receiving UE device transmits the distance-based HARQ feedback if the signal strength of a signal received from the transmitting UE device is above a threshold and does not send the HARQ feedback if the signal quality is below the threshold. The threshold may be received from the transmitting UE device.

CLAIM OF PRIORITY

The present application claims the benefit of priority to ProvisionalApplication No. 63/028,348 entitled “Groupcast Sidelink HARQ FeedbackWith No Location Information”, docket number TPRO 00349 US, filed May21, 2020, assigned to the assignee hereof and hereby expresslyincorporated by reference in its entirety.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to patent application entitled “HYBRIDAUTOMATIC REPEAT REQUEST (HARQ) FEEDBACK MANAGEMENT BASED ON LOCATIONINFORMATION AVAILABILITY FOR GROUP SIDELINK COMMUNICATION”, docketnumber TUTL 00349A PC and patent application entitled “DISTANCE-BASEDHYBRID AUTOMATIC REPEAT REQUEST (HARQ) LOCATION UNAVAILABLECONFIGURATION FOR GROUP SIDELINK COMMUNICATION”, docket number TUTL00349B PC, both filed concurrently with this application andincorporated by reference in their entirety herein.

FIELD

This invention generally relates to wireless communications and moreparticularly to hybrid automatic repeat request (HARQ) feedbackmanagement based on location information availability and sidelinksignal quality for group sidelink communication.

BACKGROUND

Many wireless communication systems that employ several base stationsthat provide wireless service to user equipment (UE) devices enablesidelink communication between two or more UE devices where the UEdevices can communicate directly with other UE devices. Such sidelinkcommunications sometimes include one UE device (group leader UE device)that transmits the same data to multiple UE devices in a group.Different transmission techniques often referred to as cast types can beused to transmit the same data to multiple UE devices. Cast typesinclude at least unicast, groupcast and broadcast. A unicasttransmission can only be received by the single UE device that is theintended recipient of the data. Accordingly, multiple transmissions arerequired to send the same data to multiple UE devices using unicast. Abroadcast transmission can typically be received by all UE deviceswithin range of the transmission. A groupcast transmission can only bereceived by the UE devices that are members of a group. Accordingly, forexample, the group leader UE device can transmit the same data in asingle transmission using groupcast to two or more UE devices in thegroup or can send the same data in multiple unicast transmissions to theUE devices.

SUMMARY

A receiving user equipment (UE) device transmits a distance-based hybridautomatic repeat request (HARQ) feedback message to a transmitting UEdevice based on sidelink signal quality when location information isunavailable. The receiving UE device is one of a group of UE devicesreceiving a groupcast data transmission from the transmitting UE devicewhere the groupcast data transmission comprises a distance-based hybridautomatic repeat request (HARQ) feedback configuration. When locationinformation is unavailable to the receiving UE device, the receiving UEdevice transmits the distance-based HARQ feedback if the measured signalquality of a signal received from the transmitting UE device is above athreshold and does not send the HARQ feedback if the signal quality isbelow the threshold. The threshold may be received from the transmittingUE device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of a communication systemincluding a first user equipment (UE) device, a second UE device, athird UE device, a fourth UE device, and two base stations.

FIG. 2 is a block diagram of an example of a communication devicesuitable for use as each of the base stations.

FIG. 3 is a block diagram of an example of a UE device suitable for useas each of the UE devices.

FIG. 4 is a message flow diagram for an example where a receiving UEdevice determines, based on signal quality, whether to transmitdistance-based HARQ feedback when location information is unavailable tothe receiving UE device.

FIG. 5 is a message flow diagram for an example where a receiving UEdevice determines whether to send distance-based HARQ messages based onSL signal quality when location information is unavailable andestablishes a unicast connection for group data.

FIG. 6 is a flow chart of an example of a method of managing groupcastfeedback based on location information availability and signal quality.

FIG. 7 is a flow chart of an example of a method of managing groupcastfeedback based on location information availability and signal quality.

DETAILED DESCRIPTION

As discussed above, different cast types can be used for communicationbetween UE devices. Although UE device groups may be formed and used indifferent situations and environments, one scenario where grouping UEdevices is particularly useful includes vehicle platoons where vehiclesdynamically form a platoon while travelling together. All the vehiclesin the platoon obtain information from the leading vehicle to manage theplatoon. In some implementations, the information facilitates travel ofthe vehicles in the same direction in a coordinated manner and allowsthe vehicles to drive closer than in normal situations where there is nocommunication between the vehicles. Vehicles of the same platoon areinvolved in sharing the necessary information required to support theplatoon operations where the information may include, for example, thedistance between vehicles, relative speeds, and updates from roadsideunits (RSUs). Similar requirements also apply to the Extended Sensor usecase where UE devices exchange data gathered through local sensors orlive video data among vehicles, RSUs, pedestrian devices, and V2Xapplication servers. Groupcast techniques allow efficient transmissionof the information from one UE device, such as the platoon leader, tothe other UE device members of the group.

In accordance with revisions of 3GPP communication specifications,sidelink communications between a transmitting UE device and receivingUE device(s) are managed with feedback messaging. In order to achievereliable communications, for example, both unicast and groupcastcommunications support hybrid automatic repeat request (HARQ) feedbackover sidelink in order for the transmitting UE device to determine ifretransmissions are needed and if the modulation code scheme (MCS) needsto be relaxed to provide a more robust retransmission to reach thereceiving peer UE device. With unicast transmissions, HARQ feedback forboth acknowledgement (ACK) and negative acknowledgement (NACK) aresupported and addressed to a single peer UE device. With groupcasttransmissions, however, the transmitting UE device configures HARQfeedback which may include ACK/NACK feedback or only NACK feedback. Thetransmitting UE device of the groupcast transmission my receive HARQfeedback from multiple peer UE devices on the Physical Sidelink FeedbackChannel (PSFCH). In order to save HARQ feedback resources on the PSFCH,the feedback for groupcast may be configured by the transmitting UEdevice for two general configurations. For a first configuration, thereceiving UE device transmits HARQ-NACK on PSFCH if it fails to decodethe corresponding transport block (TB) after decoding the associatedPSCCH. With the first configuration, the receiving UE device transmitsno signal on PSFCH otherwise. With a second configuration, the receivingUE device transmits HARQ-ACK on PSFCH if it successfully decodes thecorresponding TB and it transmits HARQ-NACK on PSFCH if it does notsuccessfully decode the corresponding TB after decoding the associatedPSCCH targeting the receiving UE device.

More specifically, when the transmitting UE device transmits data togroup member receiving UE devices, the packet consists of both thetraffic data and the header including Sidelink Control Info (SCI). TheSCI is encoded with a more robust modulation coding scheme (MCS) thanthe data so that the receiving UE devices will more easily receive thisportion of the signal. The traffic portion of the packet is encoded witha relatively less robust MCS to ensure higher data throughput.Therefore, if the receiving UE device only successfully receives thecontrol signal portion (SCI) without successfully receiving the dataportion, the receiving UE device sends a “NACK” to the transmitting UEdevice. For the option where both ACK and NACK are required forfeedback, the receiving UE device is required to send ACK when the dataportion is received successfully. When the receiving UE device cannotdecode the SCI the receiving UE device does not send either ACK norNACK. Such a situation corresponds to the HARQ DTX case where thetransmitting UE device determines that the receiving UE device did notreceive the packet if no feedback is received within a HARQ feedbacktimer.

In addition, the transmitting UE device may enable distance-based HARQfeedback. With distance-based HARQ feedback, the receiving UE devicesends HARQ feedback only if the receiving UE device is within aconfigured communication range away from the transmitting UE device.Typically, distance-based HARQ requires NACK only feedback. Forconventional systems, the transmitting UE device indicates its currentZone ID and a communication range requirement in the Sidelink ControlInfo (SCI). The receiving UE device calculates the distance from thecurrent location of the receiving UE device to the center of thatparticular Zone ID indicated in the SCI received from the transmittingUE device. If the distance is less than the communication rangerequirement, the receiving UE device sends the NACK for HARQ feedback.Therefore, when distance-based HARQ is configured, the receiving UEdevices that are far away from the transmitting UE device do not sendHARQ feedback. Such a configuration not only reduces the use of PSFCHresources, but it prevents the transmitting UE device from makingunnecessary retransmissions where a NACK is received since theretransmission will likely not be successfully received by those faraway receiving UE devices.

In some situations, location information is not available to a UEdevice. Typically, such a situation is temporary rather than an issuewith the capability of the UE device. In most situations where thetransmitting UE device does not have its own location information, thetransmitting UE device will not configure distance-based HARQ feedbackof the receiving UE devices of the group.

An issue arises when the transmitting UE device has location informationand configures distance-based HARQ feedback for groupcast transmissions,but location information is unavailable to one or more of the receivingUE devices. In this case, the receiving UE device cannot determine if itis within communication range and whether HARQ feedback should be sent.

One possible mechanism to address this problem is to require anyreceiving UE device that does not have location information to refrainfrom sending HARQ feedback if distance-based HARQ feedback isconfigured. Such a technique has the benefit that PSFCH resources can besaved for other UE devices and useless retransmissions may be avoided.In some situations, however, the receiving UE device may be well withinthe communication range but HARQ feedback cannot be sent. An example ofsuch a situation occurs when the receiving UE device passes through acoverage hole. As a result, the service performance may be unnecessarilyseverely degraded by restricting HARQ feedback even though the receivingUE device is within communication range of the transmitting UE device.

Another possible way to address the problem is to require that receivingUE devices to always send HARQ even when they do not have locationinformation and distance-based HARQ feedback is configured. Such atechnique is of course beneficial from the preserving the QoS,especially for high priority service. The technique, however, may resultin increased use of PSFCH resources and unnecessary retransmissions,especially where the receiving UE devices are outside the communicationrange and the data portion of the retransmissions is not likely to bereceived successfully. Such situations could render the HARQ feedbacksystem unusable.

Therefore, distance-based HARQ feedback management is needed forefficient transmission of HARQ feedback when location information isunavailable to a receiving UE device. For the distance-based HARQfeedback management techniques discussed herein, the receiving UE deviceeither transmits HARQ messages or refrains from transmitting HARQmessages when location information is unavailable based on signalstrength of at least one signal received from the transmitting UE deviceat the receiving UE device. For the examples herein, the transmitting UEdevice sends a location unavailable signal strength threshold message tothe receiving UE devices to configure the receiving UE devices with thethreshold. In one example, the transmitting UE device determines thethreshold. In another examples, the base station and/or network make thedetermination. In some situations, the determination is madecollaboratively by the transmitting UE device and the base stationand/or the network.

In some examples, the receiving UE device establishes a unicastconnection with transmitting UE device when the signal strength is belowthe threshold but the required quality of service (QoS) of the groupcasttransmissions is above a QoS threshold.

FIG. 1 is a block diagram of an example of a communication system 100including a first user equipment (UE) device 101, a second UE device102, a third UE device 103, a fourth UE device 104, and two basestations 106, 108. Although the techniques discussed herein may beapplied to various types of systems and communication specifications,the devices of the example operate in accordance with at least onerevision of a 3GPP New Radio (NR) V2X communication specification. Thetechniques discussed herein, therefore, may be adopted by one or morefuture revisions of communication specifications although the techniquesmay be applied to other communication specifications where sidelink orD2D is employed. More specifically the techniques may be applied tocurrent and future releases of 3GPP NR specifications. For example, thetechniques may also be applied to 3GPP NR (Rel-17). For the example, theUE devices 101-104 may be any type of device that can receive signalsfrom, and transmit signals to, base stations and other UE devices. TheUE devices operate in the communication system that includes a pluralityof base stations that each provide wireless service within a servicearea. For the example of FIG. 1 , the first UE device 101 is served by afirst base station 106 and the other UE device 102-104 are served byeither the first base station 106 or a second base station 108 and maytransition between base stations in accordance with known handovertechniques. Each of the UE devices 101-104, therefore, may be served bya different base station even though two or more UE devices arecommunicating with each other using a sidelink connection.

For the example, the first UE device 101 is a transmitting UE device andthe other UE devices 102-104 are receiving UE devices and are members ofa group. The group data for the group may be transmitted in groupcasttransmissions from the transmitting UE device 101. In some situations,the group data may be transmitted over a unicast communication link to amember of the group. For the example, a groupcast transmission 110including groupcast data is transmitted from the first UE device(transmitting UE device) 101 to the second UE device 102 and the thirdUE device 103. The group data is also sent over a unicast communicationlink to the fourth UE device 104. The first UE device 101, therefore,may also be referred to as the transmitting UE device and source UEdevice, herein. Although the example includes three UE devices 102, 103,104 in the group, the group may include any number of devices.

For the example of FIG. 1 , the fourth UE device 104 receives the groupdata in a unicast transmission 111 over unicast communication link andtherefore provides HARQ feedback in accordance with the unicastconnection. The second UE device 102 and the third UE device 103 aresent the group data over a groupcast data transmission specifying adistance-based HARQ feedback. For the example, the third UE device 103is in a situation where distance based HARQ is invoked. Morespecifically, location information is available to the third UE device103, the third UE device determines it is within the specifiedcommunication range, and the third UE device is unable to successfullyreceive the data portion of the groupcast data transmission 110. As aresult, the third UE device 103 transmits a distance-based HARQ NACKmessage 114 in accordance with the distance-based HARQ configurationestablished by the transmitting UE device 101. The HARQ messages 112,114 are transmitted over the PSFCH in accordance with known techniques.

The second UE device 102, however, does not successfully receive thedata portion of the groupcast data transmission but does not havelocation information for the example. With conventional systems, thereis no established technique for dealing with such a situation. For theexamples herein, however, the receiving UE device 102 determines whetherto transmit HARQ feedback based on the signal quality of sidelinksignals 116 received from the transmitting UE device 101. For theexamples herein, the signal quality is based on at least one of aSidelink Reference Signal Received Power (SL-RSRP). Therefore, for theexamples herein, the signal quality is determined by measuring one ormore Demodulation reference signals (DMRS) transmitted by thetransmitting UE device 101. Other techniques, however, may be used todetermine the sidelink signal quality. For the discussions herein,signal quality may include only signal strength, signal power, averagetotal received power, or signal energy. Signal quality may be based onmeasurement of over full bandwidth and/or narrow band. Also, themeasured signal may include signals other than reference signals in somecircumstances. For the example, the transmitting UE device 101determines the location unavailable signal quality threshold and sendsthe threshold to the receiving UE devices in a message 118. The locationunavailable signal quality threshold message 118 includes a SL-RSRPthreshold for the example.

After receiving the SCI in the groupcast data transmission 110 anddetermining that the data portion could not be successfully received,the second UE device 102 determines whether a HARQ message should betransmitted based on the location unavailable signal quality threshold.For the examples herein, the second UE device derives NR sidelinkmeasurement results by measuring one or multiple DMRS associatedsidelink channel as configured by the first UE device. For all NRsidelink measurement results, the second UE device applies the layer 3filtering before using the measured results for evaluation.

In one scenario, the second UE device may begin to evaluate the NRsidelink measurement continuously after it determines that locationinformation is unavailable. In another scenario, the second UE devicemay begin to evaluate the NR sidelink measurement after the groupcasttransmission is received.

Currently, the DMRS used for NR sidelink measurement is only availablewhen the first UE device has data or control signal to transmit. Thefirst UE device will not send DMRS or any other RS alone without data orcontrol signaling which is different from the Uu case. Also, currentcommunication specifications only specify SL-RSRP measurement forPC5-RRC unicast connections and not for groupcast transmissions.Accordingly, for the examples herein, the SL-RSRP measurements are inaccordance with current communication specifications except that SL-RSRPmeasurements are also available for groupcast.

If the signal quality measurements are above the signal qualitythreshold, the second UE device 102 transmits a HARQ message 120.Otherwise, no HARQ message is transmitted. The arrow representing theHARQ message is FIG. 1 is shown a dashed line to indicate that the HARQmessage 120 is transmitted in accordance with the location-unavailableconfiguration 116 and, therefore, is not transmitted in somecircumstances.

Where the SL signal quality is below the threshold, the receive UEdevice may determine that the required QoS of the groupcastcommunication is sufficient to warrant establishment of a unicastconnection to replace the groupcast link to the second UE device 102.Accordingly, in some situations, the second UE device 102 establishes aunicast link with the first UE device for the transmission of groupdata.

FIG. 2 is a block diagram of an example of a base station 200 suitablefor use as each of the base stations 106, 108. The base station 200includes a controller 204, transmitter 206, and receiver 208, as well asother electronics, hardware, and code. The base station 200 is anyfixed, mobile, or portable equipment that performs the functionsdescribed herein. The various functions and operations of the blocksdescribed with reference to the base stations 102, 104 may beimplemented in any number of devices, circuits, or elements. Two or moreof the functional blocks may be integrated in a single device, and thefunctions described as performed in any single device may be implementedover several devices. The base station 200 may be a fixed device orapparatus that is installed at a particular location at the time ofsystem deployment. Examples of such equipment include fixed basestations or fixed transceiver stations. Although the base station may bereferred to by different terms, the base station is typically referredto as a gNodeB or gNB when operating in accordance with one or morecommunication specifications of the 3GPP V2X operation. In somesituations, the base station 200 may be mobile equipment that istemporarily installed at a particular location. Some examples of suchequipment include mobile transceiver stations that may include powergenerating equipment such as electric generators, solar panels, and/orbatteries. Larger and heavier versions of such equipment may betransported by trailer. In still other situations, the base station 200may be a portable device that is not fixed to any particular location.

The controller 204 includes any combination of hardware, software,and/or firmware for executing the functions described herein as well asfacilitating the overall functionality of the base station 200. Anexample of a suitable controller 204 includes code running on amicroprocessor or processor arrangement connected to memory. Thetransmitter 206 includes electronics configured to transmit wirelesssignals. In some situations, the transmitter 206 may include multipletransmitters. The receiver 208 includes electronics configured toreceive wireless signals. In some situations, the receiver 208 mayinclude multiple receivers. The receiver 208 and transmitter 206 receiveand transmit signals, respectively, through an antenna 210. The antenna210 may include separate transmit and receive antennas. In somecircumstances, the antenna 210 may include multiple transmit and receiveantennas.

The transmitter 206 and receiver 208 in the example of FIG. 2 performradio frequency (RF) processing including modulation and demodulation.The receiver 208, therefore, may include components such as low noiseamplifiers (LNAs) and filters. The transmitter 206 may include filtersand amplifiers. Other components may include isolators, matchingcircuits, and other RF components. These components in combination orcooperation with other components perform the base station functions.The required components may depend on the particular functionalityrequired by the base station.

The transmitter 206 includes a modulator (not shown), and the receiver208 includes a demodulator (not shown). The modulator modulates thesignals to be transmitted as part of the downlink signals and can applyany one of a plurality of modulation orders. The demodulator demodulatesany uplink signals received at the base station 200 in accordance withone of a plurality of modulation orders.

The base station 200 includes a communication interface 212 fortransmitting and receiving messages with other base stations. Thecommunication interface 212 may be connected to a backhaul or networkenabling communication with other base stations. In some situations, thelink between base stations may include at least some wireless portions.The communication interface 212, therefore, may include wirelesscommunication functionality and may utilize some of the components ofthe transmitter 206 and/or receiver 208.

FIG. 3 is a block diagram of an example of a UE device 300 suitable foruse as each of the UE devices 101-104. In some examples, the UE device300 is any wireless communication device such as a mobile phone, atransceiver modem, a personal digital assistant (PDA), a tablet, or asmartphone. In other examples, the UE device 300 is a machine typecommunication (MTC) communication device or Internet-of-Things (IOT)device. The UE device 300, therefore is any fixed, mobile, or portableequipment that performs the functions described herein. The variousfunctions and operations of the blocks described with reference to UEdevice 300 may be implemented in any number of devices, circuits, orelements. Two or more of the functional blocks may be integrated in asingle device, and the functions described as performed in any singledevice may be implemented over several devices.

The UE device 300 includes at least a controller 302, a transmitter 304and a receiver 306. The controller 302 includes any combination ofhardware, software, and/or firmware for executing the functionsdescribed herein as well as facilitating the overall functionality of acommunication device. An example of a suitable controller 302 includescode running on a microprocessor or processor arrangement connected tomemory. The transmitter 304 includes electronics configured to transmitwireless signals. In some situations, the transmitter 304 may includemultiple transmitters. The receiver 306 includes electronics configuredto receive wireless signals. In some situations, the receiver 306 mayinclude multiple receivers. The receiver 304 and transmitter 306 receiveand transmit signals, respectively, through antenna 308. The antenna 308may include separate transmit and receive antennas. In somecircumstances, the antenna 308 may include multiple transmit and receiveantennas.

The transmitter 304 and receiver 306 in the example of FIG. 3 performradio frequency (RF) processing including modulation and demodulation.The receiver 304, therefore, may include components such as low noiseamplifiers (LNAs) and filters. The transmitter 306 may include filtersand amplifiers. Other components may include isolators, matchingcircuits, and other RF components. These components in combination orcooperation with other components perform the communication devicefunctions. The required components may depend on the particularfunctionality required by the communication device.

The transmitter 306 includes a modulator (not shown), and the receiver304 includes a demodulator (not shown). The modulator can apply any oneof a plurality of modulation orders to modulate the signals to betransmitted as part of the uplink signals. The demodulator demodulatesthe downlink signals in accordance with one of a plurality of modulationorders.

FIG. 4 is a message flow diagram 400 for an example where a receiving UEdevice 102 determines, based on signal quality, whether to transmitdistance-based HARQ feedback when location information is unavailable tothe receiving UE device 102.

At transmission 402, the transmitting UE device 101 sends a locationunavailable signal quality threshold message to the receiving UE device102. Transmission 402, therefore, is an example of the locationunavailable signal threshold transmission 118 discussed with referenceto FIG. 1 . The location unavailable signal threshold message providesthe signal quality threshold information to the receiving UE devicewhich is used by the receiving UE device 102 to determine whether HARQmessages for distance-based HARQ should transmitted when locationinformation is unavailable to the receiving UE device 102. For theexample, the location unavailable signal quality threshold message is aMedium Access Control (MAC) Control Element (CE) in the Sidelink ControlChannel (SCCH) transmitted in a groupcast transmission. In some cases,the location unavailable signal quality threshold message may be a PC5-S(upper layer message) delivered in the SCCH. Furthermore, the locationunavailable signal quality threshold message may be transmitted as a1-bit indicator in the SCI. In the latter case, the signal qualitythreshold value may be provided by the gNB via RRC signaling or it maybe preconfigured; therefore, only the 1-bit SCI indicator is needed toinform the receiving UE device whether to use the SL-RSRP measurementfor this purpose. Other techniques can be used to transmit the locationunavailable configuration.

At event 404, a groupcast transmission is transmitted from thetransmitting UE device 101 to the receiving UE devices of the group. Attransmission 406, the transmitting UE device 101 sends a distance-basedHARQ configuration to the receiving UE device 102 to configure thereceiving UE device for distance-based HARQ. At transmission 408, agroupcast transmission is sent by the transmitting UE device to themembers of the group. The groupcast transmission includes data and theassociated SCI. For the examples herein, the distance-based HARQconfiguration is sent in the header of a groupcast data transmission.More specifically, the HARQ configuration is sent in the SCI of thegroupcast transmission. As discussed above, the SCI is encoded with morerobust modulation coding scheme (MCS) than the data so that thereceiving UE devices will receive this portion of the signal with a muchgreater success rate. The traffic portion of the packet might be encodedwith a lesser robust MCS to ensure higher data throughput. Accordingly,for the examples herein, transmission 406 and transmission 408 are partof the same transmission at event 404. The two transmissions 406, 408are shown as separate arrows in the figures to illustrate that the SCIcan be successfully received while the data may not be successfullyreceived in some situations. For the examples, the SCI portion oftransmission 406 is successfully received and the data of transmission408 is not successfully received by the receiving UE device 102. In somesituations, information related to the HARQ configuration is transmittedover multiple channels. For example, in at least one revision of the NRV2X communication specification, the SCI is sent in two stages where afirst part is carried by the physical channel PSCCH and the second partis carried in PSSCH. As specified in Rel-16, one of the fields in thefirst stage SCI in PSCCH indicates which 2nd-stage SCI (format A or B)is used and a second stage SCI is in the PSSCH indicates eitherformat-2A for HARQ ACK/NACK and format-2B for NACK-only. The zone ID andcommunication range requirement is sent in the 2B. Accordingly, thetransmitting UE device could implicitly request the receiving UE deviceto send a distance-based HARQ by indicating the groupcast type in theSCI.

At event 410, the receiving UE device 102 determines data in thetransmission 408 was not successfully received. After successfullyreceiving the SCI portion of the groupcast transmission, the receivingUE device 102 unsuccessfully attempts to receive the data portion.

At event 412, the receiving UE device 102 determines that locationinformation is unavailable. For example, the receiving UE device 102 maydetermine that GPS service is unavailable where GPS provides theinformation required for the UE device to determine UE device location.In some situations, the location determination is performed at alocation server at the base station with assistance from the UE device.If the UE device determines that the base station cannot provide thelocation information where this technique is used, the receiving UEdevice determines that location information is unavailable.

At event 414, the receiving UE device determines whether the measuredsignal quality of the SL signals transmitted from the first UE deviceare above the signal quality threshold previously received from thetransmitting UE device 101 to determine if a HARQ message should besent. If it is determined that the HARQ message should be sent, a HARQmessage is sent at transmission 416. Otherwise, no HARQ message is sent.The arrow representing the HARQ message is shown with a dashed line inFIG. 4 to indicate that the message is not sent where the configurationdoes not include HARQ feedback messages for distance-based HARQ whenlocation information is unavailable.

FIG. 5 is a message flow diagram 500 for an example where a receiving UEdevice 102 determines whether to send distance-based HARQ messages basedon SL signal quality when location information is unavailable andestablishes a unicast connection for group data. The message flowdiscussed with reference to FIG. 5 is an example of the message flowdiscussed with reference to FIG. 4 . Transmissions 402, 406, 408 andevents 404, 410, 412 are performed as discussed above with reference toFIG. 4 .

At event 502, the receiving UE device 102 determines that the requiredQoS of the groupcast communication is above a QoS threshold. In order tomaintain the QoS above the minimum requirement, the receiving UE device102 determines that a unicast connection should replace the groupcastconnection.

At transmission 504, the receiving UE device 102 sends a DirectCommunication Request message to the transmitting UE device 101. For theexample, the Direct Communication Request message is transmitted over abroadcast channel in accordance with known techniques.

At transmission 506, the transmitting UE device 101 sends a DirectCommunication Accept message to the receiving UE device 102. For theexample, the Direct Communication Accept message is transmitted over abroadcast channel in accordance with known techniques.

At event 508, the transmitting UE device 101 removes the receiving UEdevice from the groupcast list. Accordingly, the transmitting UE device101 determines that all data associated with the group will betransmitted over the unicast link rather than in groupcasttransmissions.

At event 510, a PC5-RRC connection is established between thetransmitting UE device 101 and the receiving UE device 102. Therefore, aunicast connection is established between the two devices 101, 102.

At transmission 512, the transmitting UE device sends group data to thereceiving UE device 102 over the PC5-RRC link. The transmission 512includes the HARQ feedback configuration.

At the transmission 514, the receiving UE device 102 transmits a HARQmessage in accordance with the SCI information received in the unicasttransmission. If ACK is enabled for the transmission 512, the unicastHARQ may be an ACK. Otherwise, the transmission 514 is only NACK whenthe data portion is not successfully received.

FIG. 6 is a flow chart of an example of a method 600 of managinggroupcast feedback based on location information availability and signalquality. For the example, the method is performed by a UE deviceoperating in a NR V2X system such as the system 100 described above.Accordingly, the method may be performed by the second UE device(receiving UE device) 102 when part of a group of the first UE device(transmitting UE device) 101.

At step 601, a location unavailable signal quality threshold message isreceived from the transmitting UE device 101. As discussed above,location unavailable signal quality threshold message provides thesignal quality threshold to the receiving UE device 102 that is to beused to determine whether HARQ messages for distance-based HARQ shouldbe sent when location information is unavailable to the receiving UEdevice 102. For the example, the location unavailable signal qualitythreshold message is a Medium Access Control (MAC) Control Element (CE)in the Sidelink Control Channel (SCCH) transmitted in a groupcasttransmission. In some cases, the location unavailable signal qualitythreshold message may be a PC5-S (upper layer message) delivered in theSCCH. Furthermore, the location unavailable signal quality thresholdmessage may be transmitted as a 1-bit indicator in the SCI. In thelatter case, the signal quality threshold value may be provided by thegNB via RRC signaling or it may be preconfigured; therefore, only the1-bit SCI indicator is needed to inform the receiving UE device whetherto use the SL-RSRP measurement for this purpose. Other techniques can beused to transmit the location unavailable configuration.

At step 602, a groupcast data transmission with distance-based HARQconfiguration is received. For the example, at least the SCI portion issuccessfully received. The data portion may not be successfully receivedat step 502.

At step 604, it is determined whether the data portion of the groupcastdata transmission is successfully received. In accordance with knowntechniques, the receiving UE device 102 evaluates the information in thetransmission to determine if the data has been successfully received. Ifthe data is successfully received, the method returns to step 602 forreception of the next transmission. Otherwise, the method proceeds tostep 606.

At step 606, it is determined whether location information is available.If the location of the receiving UE device 102 is known or can bedetermined, the method continues at step 608. Otherwise, the methodproceeds to step 610.

At step 608, it is determined whether the receiving UE device 102 iswithin the distance range for sending HARQ feedback. The distance basedon the criteria specified by the transmitting UE device is calculatedand evaluated to determine if HARQ feedback is required. If thereceiving UE device is not within the distance range, the method returnsto step 602 to receive the next transmission without sending HARQfeedback. Otherwise, the HARQ feedback is transmitted at step 612. Asdiscussed above, distance-based HARQ feedback includes only NACK for theexample. Accordingly, the receiving UE device 102 sends a NACKindicating that the data in the groupcast transmission was notsuccessfully received before returning to step 602.

At step 610, the receiving UE device determines whether the measuredsignal quality of sidelink signals received from the transmitting UEdevice 101 are above the location unavailable signal quality threshold.For the examples herein, the second UE device derives NR sidelinkmeasurement results by measuring one or multiple DMRS associatedsidelink channel as configured by the first UE device. For all NRsidelink measurement results, the second UE device applies the layer 3filtering before using the measured results for evaluation.

In one scenario, the second UE device may begin to evaluate the NRsidelink measurement continuously after it determines that locationinformation is unavailable. In another scenario, the second UE devicemay begin to evaluate the NR sidelink measurement after the groupcasttransmission is received.

If the measured signal quality is above the threshold, the methodproceeds to step 612 where a HARQ message is transmitted. Otherwise, themethod continues at step 614 where the receiving UE device refrains fromsending HARQ feedback.

For the example, the method then continues to step 616 where it isdetermined whether the required QoS of the groupcast is above a QoSthreshold. If the required QoS of the groupcast is above the QoSthreshold, the method proceeds to step 618. Otherwise, the methodreturns to step 602 where a new groupcast message is received. In somesituations, the method returns to step 601 to receive a new locationunavailable signal quality threshold before receiving the next groupcastmessage at step 602.

At step 618, a unicast connection is established for the group data. Thegroupcast connection is, therefore, replaced with a unicast connectionto improve quality of the connection for receiving the group data.

FIG. 7 is a flow chart of an example of a method 700 of managinggroupcast feedback based on location information availability using asignal quality threshold. For the example, the method is performed by aUE device operating in a NR V2X system such as the system 100 describedabove. Accordingly, the method may be performed by the first UE device(transmitting UE device) 101 when transmitting groupcast transmission toa group of UE devices including the second UE device (receiving UEdevice) 102.

At step 702, it is determined whether distance-based HARQ will be usedfor groupcast messages. The transmitting UE device evaluates factorssuch as the QoS, number of UE devices in the group, and the availablePSFCH resources. If it is determined that distance-based HARQ feedbackshould be used, the method continues at step 704. Otherwise, the methodproceeds to step 706 where groupcast data is transmitted in a groupcasttransmission with a groupcast HARQ not based on distance configuration.

At step 704, the location unavailable signal quality threshold isdetermined. For the example, the transmitting UE device 101 evaluatesfactors such as the QoS, number of UE devices in the group, and theavailable PSFCH resources to determine what signal threshold a receivingUE device should use in determining whether to transmit HARQ messageswhen location information is unavailable. In some situations, thedetermination on what threshold should be used by a receiving UE devicethat does not have location information is at least partially performedby a base station or the network. Accordingly, the transmitting UEdevice 101 may provide information to the serving base station andreceive instructions on determining the threshold or the actualthreshold value that should be used when location information isunavailable. Also, the base station may provide criteria or informationthat assists the transmitting UE device in determining the locationunavailable signal quality threshold.

At step 708, the location unavailable signal quality threshold istransmitted to the receiving UE devices. As discussed above, thelocation unavailable signal quality threshold is the threshold that isto be used by receiving UE devices. Accordingly, the threshold indicatesallows the UE device to determine whether the receiving UE devicetransmits a HARQ message for data transmitted with a distance-based HARQwhen the receiving UE device 102 does not know its location. For theexample, the location unavailable signal quality threshold message is aMedium Access Control (MAC) Control Element (CE) in the Sidelink ControlChannel (SCCH) transmitted in a groupcast transmission. In some cases,the location unavailable signal quality threshold message may be a PC5-S(upper layer message) delivered in the SCCH. As discussed above, thelocation unavailable signal quality threshold message may be transmittedas a 1-bit indicator in the SCI. Other techniques can be used totransmit the location unavailable configuration.

At step 710, a groupcast data transmission with distance-based HARQconfiguration is transmitted to a group of UE device including thesecond UE device (receiving UE device 102. The groupcast datatransmission includes distance-based HARQ feedback configuration.

At step 712, it is determined whether the groupcast transmissions to theUE devices should continue to use distance-based HARQ or if the HARQfeedback should be switched to HARQ feedback that is not based ondistance. The transmitting UE device evaluates factors such as the QoS,number of UE devices in the group, and the available PSFCH resources. Ifit is determined that distance-based HARQ feedback should continue to beused, the method continues at step 714. Otherwise, the method proceedsto step 706 where the next groupcast transmission uses HARQ feedbackthat is not based on distance.

At step 714, it is determined whether a new location unavailable signalquality threshold should be used for groupcast transmissions usingdistance-based HARQ. The transmitting UE device 101 evaluates factorssuch the QoS required for the receiving UE device, available resourcesand the number of UE devices in the group to determine if the thresholdshould be changed from the previous transmission. If no change inthreshold is required, the method returns to step 710 where thetransmitting UE device 101 transmits the next groupcast transmission. Ifa threshold change is required, the method returns to step 704 where thenew threshold is determined. For the example of FIG. 7 , therefore, anew location unavailable signal quality threshold is transmitted onlywhere the threshold has changed from the previous transmission. In somesituations, however, the location unavailable signal quality thresholdis transmitted with each groupcast transmission. Other techniques mayalso be used.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. The above description is illustrative and not restrictive.This invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and accompanying drawings. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

1. A method performed at a receiving user equipment (UE) device, themethod comprising: receiving a groupcast data transmission from atransmitting UE device, the groupcast data transmission comprising adistance-based hybrid automatic repeat request (HARQ) feedbackconfiguration; determining that a HARQ feedback message is required inresponse to the groupcast data transmission; determining that locationinformation is unavailable; and determining whether the HARQ feedbackmessage is sent at least partially based on a relationship of a measuredsignal quality of a sidelink signal transmitted by the transmitting UEdevice to the location unavailable signal quality threshold.
 2. Themethod of claim 1, further comprising: transmitting the HARQ feedbackmessage when the measured signal quality meets the location unavailablesignal quality threshold; and refraining from transmitting the HARQfeedback message when the measured signal quality does not meet thelocation unavailable signal quality threshold.
 3. The method of claim 2,wherein determining whether the HARQ feedback message is sent comprises:determining whether the measured signal quality is greater than thelocation unavailable signal quality threshold; sending the HARQ feedbackmessage when the measured signal quality is greater than the locationunavailable signal quality threshold; and refraining from sending theHARQ feedback message when the measured signal quality is not greaterthan the location unavailable signal quality threshold.
 4. The method ofclaim 1, wherein the sidelink signal is a reference signal.
 5. Themethod of claim 4, wherein the location unavailable signal qualitythreshold comprises a Sidelink Reference Signal Received Power(SL-RSRP).
 6. The method of claim 4, wherein the reference signal isDemodulation Reference Signals (DMRS)
 7. The method of claim 1, furthercomprising: in response to determining that the HARQ feedback messageshould not be sent, determining whether a unicast connection should beestablished for receiving group data from the transmitting UE device. 8.The method of claim 7, wherein determining whether the unicastconnection should be established comprises determining whether arequired quality of service (QoS) of groupcast transmissions from thetransmitting UE device is greater than a QoS threshold, the methodfurther comprising: in response to determining that the unicastconnection should be established, broadcasting a Direct CommunicationRequest to the transmitting UE device.
 9. The method of claim 1, furthercomprising: receiving the location unavailable signal quality thresholdfrom the transmitting UE device.
 10. The method of claim 9, whereinreceiving the location unavailable signal quality threshold comprisesreceiving a Sidelink Control Channel (SCCH) signal transmitted in agroupcast transmission.
 11. The method of claim 10, wherein receivingthe location unavailable signal quality threshold comprises receiving aMedium Access Control (MAC) Control Element (CE) in the SCCH signaltransmitted in the groupcast transmission.
 12. A receiving userequipment (UE) device comprising: a receiver configured to receive agroupcast data transmission from a transmitting UE device, the groupcastdata transmission comprising a distance-based hybrid automatic repeatrequest (HARQ) feedback configuration; a controller configured to:determine that a HARQ feedback message is required in response to thegroupcast data transmission; determine that location information isunavailable; and determine whether the HARQ feedback message is sent atleast partially based on a relationship of a measured signal quality ofa sidelink signal transmitted by the transmitting UE device to thelocation unavailable signal quality threshold.
 13. The receiving UEdevice of claim 12, further comprising: a transmitter configured totransmit the HARQ feedback message when the measured signal qualitymeets the location unavailable signal quality threshold and refrain fromtransmitting the HARQ feedback message when the measured signal qualitydoes not meet the location unavailable signal quality threshold.
 14. Thereceiving UE device of claim 13, wherein controller is configured todetermine whether the HARQ feedback message is sent by at leastdetermining whether the measured signal quality is greater than thelocation unavailable signal quality threshold, the transmitterconfigured to: transmit the HARQ feedback message when the measuredsignal quality is greater than the location unavailable signal qualitythreshold; and refrain from sending the HARQ feedback message when themeasured signal quality is not greater than the location unavailablesignal quality threshold.
 15. The receiving UE device of claim 12,wherein the sidelink signal is a reference signal.
 16. The receiving UEdevice of claim 15, wherein the location unavailable signal qualitythreshold comprises a Sidelink Reference Signal Received Power(SL-RSRP).
 17. The receiving UE device of claim 12, wherein thecontroller is further configured to, in response to determining that theHARQ feedback message should not be sent, determining whether a unicastconnection should be established for receiving group data from thetransmitting UE device.
 18. The receiving UE device of claim 17, whereinthe controller is configured to determine whether the unicast connectionshould be established by at least determining whether a required qualityof service (QoS) of groupcast transmissions from the transmitting UEdevice is greater than a QoS threshold, the transmitter configured tobroadcast a Direct Communication Request to the transmitting UE devicein response to a determination that the unicast connection should beestablished.
 19. The receiving UE device of claim 12, wherein thereceiver is configured to receive the location unavailable signalquality threshold from the transmitting UE device.
 20. The receiving UEdevice of claim 19, wherein the receiver is configured to receive thelocation unavailable signal quality threshold by at least receiving aSidelink Control Channel (SCCH) signal transmitted in a groupcasttransmission.
 21. The receiving UE device of claim 20, wherein thereceiver is configured to receive the location unavailable signalquality threshold by at least receiving a Medium Access Control (MAC)Control Element (CE) in the SCCH signal transmitted in the groupcasttransmission.
 22. A transmitting user equipment (UE) device comprising:a controller configured to determine a location unavailable signalquality threshold for a receiving user equipment (UE) device, thelocation unavailable signal quality threshold for determining whetherthe receiving UE device transmits a HARQ message in response to agroupcast transmission using a distance-based hybrid automatic repeatrequest (HARQ) feedback configuration when location information isunavailable to the receiving UE device; and a transmitter configured totransmit the location unavailable signal quality threshold to thereceiving UE device.
 23. The transmitting UE device of claim 22, whereinthe controller is configured to determine the location unavailablesignal quality threshold at partially based on information received froma base station serving the transmitting UE device.
 24. The transmittingUE device of claim 22, wherein the controller is configured to determinethe location unavailable signal quality threshold at partially based onat least one of: a quality of service (QoS) of communications with thereceiving UE device, a number of UE devices in a group receiving thegroupcast transmission, and available Physical Sidelink Feedback Channel(PSFCH) resources.
 25. The transmitting UE device of claim 22, whereinthe transmitter is configured to transmit the location unavailablesignal quality threshold by transmitting an a Medium Access Control(MAC) Control Element (CE) in the Sidelink Control Channel (SCCH) signaltransmitted in a groupcast transmission.
 26. The transmitting UE deviceof claim 24, wherein the SCCH signal is transmitted in accordance withat least one revision least one revision of a Third GenerationPartnership Project (3GPP) New Radio (NR) V2X communicationspecification.